A wide variety of consumer and commercial products such as; ingestible products; food; health care products; personal care products; household products; or garage products and the like, are packaged and sold to consumers in many different types of rigid and semi rigid containers. These containers can vary in size and shape, but generally consist of a tubular body portion with a bottom end sealed by a wall end. The opposite top end incorporates an open mouth that includes means for securing a closure cap. The mouth opening ends with an exterior rim, perpendicular to the bore of the container, that provides a surface area for sealing the opening with the closure cap. These containers can be constructed from one or more types of material such as; plastic; glass; metal; or paperboard.
Many of the products that are packaged and sold to consumers in these containers require the container to have, in addition to the closure cap, a closure seal that serves a number of practical and important functions such as; maintaining a hermetic seal to keep air, moisture, and contaminants away from the product; to prevent any leakage; and also to prevent tampering with the container contents by leaving telltale evidence when the seal has been removed.
The packaging industry has developed a wide variety of seals and sealing methods to fulfill these requirements such as; seals that are bonded to the container rim by pressure sensitive, evaporative, or reactive adhesives; seals that are thermally bonded to the container rim with a hot melt adhesive that is activated by an external heat source; or, most commonly, seals that are thermally bonded to the container rim with a hot melt adhesive that is activated by induction sealing.
Induction seals generally consist of a layer of metal foil sheet material that has one side coated with a layer of hot melt adhesive. The opposite side of the foil layer can be bonded to a variety of additional sheet materials such as; releasable stiffeners; permanent stiffeners; or resealing liners, etc. Finished seal disks are die cut from prefabricated rolls of this varied composite sheet material and inserted into the closure cap which is then installed over the container opening by press fit or complimentary screw threads. The installed closure cap presses the hot melt adhesive side of the inserted seal disk against the container rim. The container is then passed through an induction sealer that generates a high voltage discharge which is conducted by the metal foil layer of the seal causing it to heat up. The hot foil layer in turn melts the hot melt adhesive layer which bonds the seal to the container rim.
Induction sealing is well known and widely used through out the packaging industry. It provides many advantages and benefits over other sealing methods such as:                Induction seals provide a low cost, leak proof closure that is reliable and can be manufactured and installed at high speed.        The hot melt adhesive layer creates a bond between the seal and the container rim that is stronger than the seal itself which forces the seal to tear along the inside perimeter of the rim when the seal is broken and pulled from the container opening. This leaves the peripheral portion of the seal bonded to the container rim thereby indicating to a consumer that the seal has been removed and the contents may have been tampered with.        The seal is destroyed during the opening procedure which prevents the seal from being able to be reinstalled on the container after its removal.        
However, the same material properties and performance characteristics that provide induction seals with advantages over other sealing methods such as strength, durability, and ease of installation, also, by nature, create considerable drawbacks.
The combination of the metal foil layer together with the hot melt adhesive layer produces a seal of substantial strength. Although a strong seal is desirable, the strength of the multi layered construction also makes the installed seal extremely difficult to break open and remove from the container. The amount of force required to initiate a tear in a typical induction seal so it can be pinched and removed from the container opening cannot be easily applied by a consumer forcing a finger into the seal to break it. A sharp opening device such as a knife is usually needed to first cut an opening in the seal. This allows the consumer to then insert a finger into the opening so that the seal can be pinched between the consumers fingers and then pulled from the container. Even after the seal is cut open, its high tear resistance often makes it difficult for many consumers to apply enough pinching force to pull and tear the seal from the container without the seal slipping out from between the consumers fingers. The high strength bond created by the hot melt adhesive also prevents the seal from being able to be pulled from the rim by pinching and pulling the small area of the seal that may overhang the rim of the container.
These drawbacks are well known and present a number of significant disadvantages for the consumer such as:                The need to provide a sharp device such as a knife in order to cut open the seal is an inconvenience.        Portions of the seal material may tear away when the seal is either being cut, broken open, or pulled from the container which could contaminate the container contents.        The consumer could be cut by either the sharp opening device when attempting to cut the seal or, by the jagged edge of the cut foil itself while attempting to pinch and pull the seal from the container opening.        The peripheral portion of the seal remains bonded to the container rim, which prevents the container from being able to be cleanly recycled.        
To overcome these well known disadvantages the packaging industry has developed and been granted numerous patents for container closure seals that include various types of integral openers that provide for the tool free removal of the seal from the container by either initiating a tear in the seal, or by the ability of the integral opener to remove the entire seal, or a portion of it, from the container when the opener is pulled by a consumer.
A first method of providing a container closure seal with an integral opener is by including a peripheral pull tab. The tab protrudes from the periphery of the seal and is usually formed from a portion of the seal material itself when the seal is die cut. The tab is large enough to be pinched by a consumer which then allows the seal to be pulled from the container. These pull tabs require the seal to use an adhesive with a bond strength that is weaker than the strength of the seal material which allows the seal to release from the container rim before the tab tears from the seal.
A crowded field of prior art patents disclose numerous variations of peripheral pull tabs that allow for the removal of a sealing closure from a container such as shown in U.S. Patents: U.S. Pat. No. 6,474,490 to Seibel; U.S. Pat. No. 5,927,530 to Moore; U.S. Pat. No. 5,915,578 to Burt; U.S. Pat. No. 5,887,738 to Bietzer; U.S. Pat. No. 5,860,544 to Brucker; U.S. Pat. No. 5,797,509 to Fitch; U.S. Pat. No. 5,720,401 to Moore; U.S. Pat. No. 5,664,694 to Bietzer et. al.; U.S. Pat. No. 5,551,608 to Moore et. al.; U.S. Pat. No. 5,513,781 to Ullrich; U.S. Pat. No. 5,415,306 to Luch et. al.; U.S. Pat. No. 5,372,268 to Han; U.S. Pat. No. 5,341,948 to Gaeta; U.S. Pat. No. 5,197,618 to Goth; U.S. Pat. No. 5,184,746 to Moore et. al.; U.S. Pat. No. 5,176,271 to Painchaud et. al.; U.S. Pat. No. 5,156,286 to Piccard; U.S. Pat. No. 5,121,845 to Blanchard; U.S. Pat. No. 5,119,964 to Witt; U.S. Pat. No. 5,012,946 to McCarthy; U.S. Pat. No. 4,981,229 to Lanham; U.S. Pat. No. 4,890,758 to Gailus; U.S. Pat. No. 4,872,571 to Crecelius et. al.; U.S. Pat. No. 4,869,383 to Bahr et. al.; U.S. Pat. No. 4,863,061 to Moore; U.S. Pat. No. 4,778,698 to Ou-Yang; U.S. Pat. No. 4,760,931 to Gach; U.S. Pat. No. 4,754,890 to Ullman; U.S. Pat. No. 4,739,891 to Bullock, III; U.S. Pat. No. 4,727,999 to Gach; U.S. Pat. No. 4,724,978 to Cleevely et. al.; U.S. Pat. No. 4,722,447 to Crisci; U.S. Pat. No. 4,682,702 to Gach; U.S. Pat. No. 4,637,519 to Dutt et. al.; U.S. Pat. No. 4,625,875 to Carr et. al.; U.S. Pat. No. 4,523,689 to Laub; U.S. Pat. No. 4,209,126 to Elias; U.S. Pat. No. 3,988,185 to Johnson et. al; U.S. Pat. No. 3,961,566 to Westphal et. al.; U.S. Pat. No. 3,900,125 to Wyler et. al.; U.S. Pat. No. 3,632,004 to Grimes; U.S. Pat. No. 3,501,042 to Risch; U.S. Pat. No. 2,925,188 to Grumbles; and U.S. Pat. No. 749,423 to Chapman.
Although a peripheral pull tab provides the means for removing a closure seal from a container, the presence of the tab itself also creates a number of hindrances to the efficient fabrication and installation of the seal.
As stated induction sealing generally requires that the seal first be inserted into the closure cap. However, when a peripherally tabbed seal is pushed into the closure cap, the protruding tab is left positioned at a right angle up against the inner sidewall of the cap. If the tab is left in this position, it will most likely pleat and crimp together as the cap is press fit or torqued on to the container by complimentary screw threads which will prevent the proper installation of both the cap and the seal. If an installation procedure can be used that successfully leaves the tab in the correct position, squeezed between the cap and the side of the container just below the rim, the same adhesive coating that bonds the seal to the rim will also bond the tab to the container during the induction sealing process. This prevents the tab from being able to be lifted up to pull the seal from the container when the cap is removed.
One method disclosed in the prior art to overcome these drawbacks is to fold the protruding tab back over on top of the seal prior to inserting the seal into the cap. However, inserting the seal into the closure cap with the tab folded back also brings the adhesive layer on the tab into contact with the underside of the cap which will cause the tab to bond to the inside of the cap when the seal is heated in the induction sealing process. To prevent this requires the use of an additional liner that is inserted into the cap prior to the seal that consists of a material that does not adhere to the adhesive layer on the tab when the seal is heated.
Other methods of preventing the tab from interfering with the insertion of the seal into the cap or the installation of the cap and the seal onto the container are also disclosed in the prior art such as:                Including vertical grooves in either the cap or down the sidewall of the container adjacent to the rim for the tab to seat into.        Angling outwardly an upper portion of the inner sidewall of the cap which prevents the tab from coming into contact with, and bonding to, the container neck.        And various other methods of folding the tab etc.        
Irrespective of the numerous design schemes disclosed in the prior art that attempt to perfect the manufacture and installation of a peripherally tabbed induction seal, a common and more intractable problem exists. During the induction heat sealing process the additional mass and uneven shape of the metal foil tab creates eddies in the induced high voltage current as it flows through the foil layer of the seal. These eddies cause the foil layer to heat unevenly which can prevent portions of the seal from completely bonding to the container rim. This phenomena is well known and understood by those skilled in the art. To minimize incomplete bonding of the seal requires that a number of variables in the induction sealing process and the fabrication of the seal must be kept within exact specifications, such as keeping the tab as small as possible. However, even with rigid quality and process control the problem of incomplete bonding of peripherally tabbed induction seals is still observed.
To overcome these drawbacks, manufacturers have developed a second type of pull open closure seal. The pull opener consists of various lift up tabs, pull rings, or pull members that are attached to the outer surface of the seal. Some of these openers may also be attached to the closure cap itself. These pull openers require the seal to use an adhesive with a bond strength that is weaker than the strength of the pull opener which allows the seal to release from the rim without the pull opener breaking or tearing from the seal. These various types of openers allow a consumer to remove the entire seal, or a portion of it, from the container which then allows the remainder of the seal to be removed from the container opening.
Again a crowded field of prior art patents disclose numerous variations of integral lift tabs or other pull openers that are attached to the outer surface of the seal and allow for the removal of a seal from a container rim such as shown in U.S. Patents: U.S. Pat. No. 6,461,714 to Giles; U.S. Pat. No. 6,179,147 to Mogard et. al.; U.S. Pat. No. 6,082,568 to Flanagan; U.S. Pat. No. 5,887,747 to Burklin et. al.; U.S. Pat. No. 5,702,015 to Giles; U.S. Pat. No. 5,560,989 to Han; U.S. Pat. No. 5,514,442 to Galda; U.S. Pat. No. 5,433,992 to Galda; U.S. Pat. No. 5,265,745 to Pereyra; U.S. Pat. No. 5,004,111 to McCarthy; U.S. Pat. No. 4,961,986 to Galda et. al.; U.S. Pat. No. 4,960,216 to Giles; U.S. Pat. No. 4,934,544 to Han; U.S. Pat. No. 4,863,047 to Crow; U.S. Pat. No. 4,819,819 to Robertson, Jr.; U.S. Pat. No. 4,815,618 to Gach; and U.S. Pat. No. 4,739,892 to Tudek; U.S. Pat. No. 4,126,245 to Baroody.
Although this second group of prior art seal designs incorporate various pull openers that overcome many of the disadvantages associated with prior art seals that use peripheral pull tabs, one drawback is that they generally require an increase in the number of manufacturing steps and a not insignificant increase in the amount of additional materials necessary to fabricate the opener, which can add substantially to the cost of the seal.
In addition to the various drawbacks associated with the many variations of the prior art pull open and non pull open induction seals, and summarized herein, an additional drawback of a more serious nature exists with pull open seals in general when the seal is to serve in a tamper evident capacity.
As stated, the installation of an induction seal is based upon heating the metal foil layer to a temperature sufficient to melt the adhesive layer, which after cooling, bonds the seal to the container rim. However, the drawback of using a hot melt type adhesive is that it also allows the installed seal to be easily removed from the container rim intact by simply reapplying sufficient heat to the seal. Additionally, with many prior art pull open type induction seals it is not even necessary to reapply heat to remove the seal intact since the integral opener often leaves the seal in an undamaged state after its removal from the container rim. In either case the intact seal can then be reinstalled on the same container by either reapplying sufficient heat or by applying a compatible adhesive to the seal.
A container seal that can be removed and then replaced in this manner allows a malicious person intending to do harm to another, to adulterate the contents of the container without leaving any evidence of such adulteration. If the seal is required to serve in a tamper evident capacity by leaving a telltale sign that it has been removed, as would be the case with ingestible or personal care products, the relative ease with which this safety feature can be circumvented could have serious consequences for the consumer and the packager of the product. Consequently, a need still exists for an pull open tamper evident seal that overcomes the aforementioned deficiencies and drawbacks inherent in prior art pull open and non pull open induction seals.
It is in this context that the tamper evident pull open seal of my present invention assumes significance.